Field: The invention pertains to processes for recovering copper from iron-containing, copper ore materials as mined and smelted.
Objective: It was a principal objective in the making of this invention to improve the recovery of copper values from an iron-containing, copper ore mining and smelting operation.
State of the Art: Slag wastes from copper smelting facilities are substantially homogeneous materials which typically contain from about 0.6% to about 1.0% copper by weight and sometimes more. Heretofore, attempts have been made to recover metallic values from the slag wastes. For example, U.S. Pat. No. 3,273,997 discloses a nonselective process for recovering soluble iron, lead, copper, calcium, silicon, zinc, and aluminum values contained in slag waste by mixing a warm, concentrated solution of a mineral acid with the crushed slag, separating the resulting solution from the solid, insoluble residue, and recovering the soluble metals from the solution. The temperature of the mixed solution and slag must be maintained at less than 175.degree. F. to avoid formation of silica gel therein.
A method of leaching copper ores with a solution of ferric sulfate and sulfuric acid is disclosed in U.S. Pat. No. 2,563,623. It is taught that the total iron content of the leach solution must be maintained at a value less than 10 grams per liter and that the pH of the solution must be controlled at less than 2, to prevent plugging of the flow channels in the ore body with precipitated iron salts.
In U.S. Pat. No. 1,451,734, it is taught that the leaching action of an acidic, ferric-containing solution on copper ore can be increased by recycling to fresh ore after first passing the solution through a body of pyrite. The patent also teaches that this treatment causes excessive buildup of ferric ion in solution, so that passing of the resulting pregnant solution through a bed of manganese ore is required in order to reduce ferric iron content prior to copper recovery.
A publication by T. R. Shelley entitled "Possible Methods for Recovering Copper from Waste Copper Smelting Slags by Leaching", Institution of Mining and Metallurgy Transactions, Section C, 3/75, pp. C1-C4, describes this experimental leaching at Arya Mehr University of Technology, Teheran, Iran, of a blast-furnance smelter slag with a leaching solution prepared by dissolving iron powder in sulfuric acid, as compared with similar leaching of the slag with an ammonia-ammonium carbonate solution. Problems of gelification were encountered in the acidic ferric sulfate leaching and the ammonia-ammonium carbonate leach was recommended.